Variable displacement compressor

ABSTRACT

A variable displacement compressor capable of controlling a piston stroke by openably controlling a displacement control valve to regulate a pressure in a crank chamber, comprising the displacement control valve disposed in a passageway from a discharge chamber to the crank chamber, and a fixed orifice provided in a passageway from the crank chamber to a suction chamber, the displacement control valve further comprising a pressure sensing member for the pressure in the suction chamber or the crank chamber, a valve element having a valve part opened and closed in response to the operation of the pressure sensing member, a valve chamber for disposing the valve part therein and allowing the pressure in the crank chamber to act therein, a partition wall disposed around the valve element, a pressure chamber partitioned from the valve chamber by the partition wall and allowing the pressure in the suction chamber to act therein, and a solenoid provided to the other end of the valve element, wherein a flow passage of non-contact structure is formed in the partition wall, and the number of sliding parts is reduced to lower a sliding resistance.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a variable displacement compressor usedin an air conditioning system for vehicles, etc., and specifically to avariable displacement compressor capable of allowing a smooth operationof a displacement control valve at a high reliability and capable ofsimplifying the processing of the compressor as a whole.

BACKGROUND ART OF THE INVENTION

As a variable displacement compressor provided in a refrigerationcircuit of an air conditioning system for vehicles, etc., a compressorsuch as one disclosed in JP-A-11-107929 is known. To this variabledisplacement compressor, in order to control its displacement fordischarge, a displacement control valve is provided, in which a controlpoint for a pressure in a suction chamber is decided to be one-to-onerelative to an amount of electricity applied to an electromagneticactuator, and which can maintain the variable displacement compressorforcibly at a minimum displacement condition when it is not excited.

This displacement control valve is structured as depicted in FIG. 4, andit comprises a valve casing 111, a bellows 112 as a pressure sensingmember for sensing a pressure in a suction chamber or a crank chamberwhich is disposed in valve casing 111 and in which a spring 112 a isdisposed at a vacuum condition therein, a guide 113 receiving the lowerend of bellows 112 and supported movably by valve casing 111, a spring114 urging guide 113 upward, an adjustment screw 115 forming a part ofvalve casing 111 for adjusting an amount of expansion/contraction ofbellows 112, a transmission rod 116 being brought into contact with theupper end of bellows 112 and supported movably by valve casing 111, avalve element 118 being brought into contact with the other end oftransmission rod 116 and opening and closing a communication passage 117between a discharge chamber and the crank chamber of the variabledisplacement compressor in response to the expansion/contraction ofbellows 112, and an electromagnetic coil 121 generating anelectromagnetic force for urging valve element 118 in its valve openingdirection via a plunger 119 slid in a housing 110 and a transmission rod120 slid in a fixed iron core 121 a.

Further, a surface 118 b of valve element 118 opposite to a contactsurface 118 a being brought into contact with the valve seat is formedso as to receive a pressure in a crank chamber through a pressureguiding passage 122. A pressure receiving area for a pressure in a crankchamber of contact surface 118 a side of valve element 118 and apressure receiving area for a pressure in a crank chamber of surface 118b opposite thereto are set at almost the same area. Further, a sidesurface 118 c of valve element 118 is supported movably by valve casing111, a gap between the side surface 118 c and the inner circumferentialsurface of valve casing 111 is set very small, and in this portion,valve element 118 is substantially slid in its axial direction.

In the above-described mechanism of the displacement control valve ofthe variable displacement compressor, although a pressure in a crankchamber is controlled by moving and controlling valve element in itsaxial direction, thereby controlling the displacement for discharge,totally four sliding parts between transmission rod 116 and valve casing111, between side surface 118 c of valve element 118 and valve casing111, between transmission rod 120 and fixed iron core 121 a and betweenplunger 119 and housing 110 are present in this mechanism for movementand control in the axial direction of valve element 118. Therefore, whenvalve element 118 is moved and controlled in its axial direction,because there occur sliding resistances in the respective sliding parts,if these sliding resistances are great, there is a fear to deterioratethe movement of valve element 118. Moreover, because four sliding partsare arranged in the same axial direction, it may be difficult tomaintain the respective sliding parts accurately at respectivepredetermined positional relationships without shifting, and also fromthis point of view, there is a fear to enlarge the sliding resistance.If the movement of valve element 118 is deteriorated by such a slidingresistance, a smooth control of displacement for discharge of thevariable displacement compressor may be damaged.

DISCLOSURE OF THE INVENTION

Accordingly, an object of the present invention is to provide a variabledisplacement compressor which can reduce a sliding resistanceaccompanying with the movement of a valve element of a displacementcontrol valve, thereby controlling displacement for discharge smoothly.

Another object of the present invention is to provide a structurewherein, in addition to the above-described structure for reducing thesliding resistance, it is possible to form a fixed orifice, which hasbeen formed at a cylinder block side or the vicinity thereof andprovided at a position in a pressure relief passageway communicatingfrom a crank chamber to a suction chamber, in a displacement controlvalve, thereby simplifying the processing, in particular, simplifyingthe processing of the cylinder block side.

To achieve the above objects, a variable displacement compressoraccording to the present invention has a discharge chamber, a suctionchamber and a crank chamber, the compressor comprises a displacementcontrol valve disposed at a position in a discharge pressure supplypassageway capable of communicating with the crank chamber from thedischarge chamber, and a fixed orifice provided at a position in apressure relief passageway communicating with the suction chamber fromthe crank chamber, the displacement control valve is controlled inopening/closing operation to regulate a pressure in the crank chamber tocontrol a piston stroke, wherein the displacement control valve furthercomprises a pressure sensing member being expanded and contracted bysensing a pressure in the suction chamber or the crank chamber, a valveelement one end of which is brought into contact with the pressuresensing member and which has a valve part opening and closing a valvehole formed in the discharge pressure supply passageway in response toan expansion/contraction of the pressure sensing member, a valve chamberin which the valve part is disposed and to which a pressure in the crankchamber acts, a partition wall disposed around the valve element at aposition in an axial direction of the valve element, a pressure chamberwhich is partitioned from the valve chamber by the partition wall and towhich a pressure in the suction chamber acts, and a solenoid provided tothe other end of the valve element and capable of controlling an openingdegree of the valve part by increase/decrease of an electromagneticforce, and a flow passage from the valve chamber to the pressure chamberis formed in a portion disposed with the partition wall, whereby a gapis defined for forming a non-contact structure which does not give asliding resistance relative to a movement of the valve element in itsaxial direction.

Namely, in this structure, a conventional sliding part having beenpresent in the portion of the partition wall is abolished, and a gapwith a non-contact structure is formed and this gap is positivelyutilized as a flow passage from the valve chamber to the pressurechamber. By this structure, the number of the conventional four slidingparts as aforementioned can be surely reduced by at least one.

In this variable displacement compressor, the above-described gap may beformed as the fixed orifice, and by this, the fixed orifice may beformed in the displacement control valve and it is not necessary to formit at another portion.

Further, the above-described partition wall may be fixed at a valvecasing side of the displacement control valve, and the above-describedgap may be defined between an inner circumferential surface of thepartition wall and an outer circumferential surface of the valveelement. Alternatively, the partition wall may be fixed to the valveelement, and the gap may be defined between an outer circumferentialsurface of the partition wall and an inner circumferential surface of avalve casing of the displacement control valve.

Moreover, it is preferred to employ a structure wherein the solenoidcomprises an electromagnetic coil excited for generating anelectromagnetic force, a fixed iron core for generating a magnetic forceby excitation of the electromagnetic coil, and a plunger attracted andmoved to fixed iron core side by the magnetic force of the fixed ironcore, and in this structure, the other end of the valve element is fixedto the plunger, the plunger is held slidably in an axial direction ofthe valve element, and a gap is defined between the fixed iron core andthe valve element for forming a non-contact structure which does notgive a sliding resistance relative to a movement of the valve element inits axial direction. By this, the sliding parts present in therespective portions of the fixed iron core and the plunger in theaforementioned conventional structure may become only a sliding part ofthe plunger. Therefore, in this structure, the number of theconventional four sliding parts becomes totally two, namely, the slidingparts in the axially extending portion of the valve element includingthe plunger become only two sliding parts at both end portions(two-point suspension), and even from the viewpoint of the principle ofsupporting mechanism, a smooth operation of the movement of the valveelement may be assured.

Thus, in the variable displacement compressor according to the presentinvention, since a non-contact gap structure is formed at a portion ofthe partition wall and generation of a sliding resistance is preventedat this portion, and the number of sliding parts may be reduced also inthe solenoid side, the sliding resistance accompanying with the movementof the valve element may be greatly reduced, and a stable and smoothcontrol of displacement for discharge may be achieved by the smoothoperation of the valve element.

Further, because the gap in the partition wall may be formed as thefixed orifice, it becomes unnecessary to provide the fixed orifice atanother portion of the compressor, thereby simplifying the processing ofthe cylinder block and its vicinity portion and reducing the cost as awhole.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of a variable displacementcompressor according to a first embodiment of the present invention.

FIG. 2 is an enlarged vertical sectional view of a portion of adisplacement control valve of the variable displacement compressordepicted in FIG. 1.

FIG. 3 is a vertical sectional view of a portion of a displacementcontrol valve of a variable displacement compressor according to asecond embodiment of the present invention.

FIG. 4 is a vertical sectional view of a portion of a displacementcontrol valve of a conventional variable displacement compressor.

THE BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, desirable embodiments of the present invention will beexplained referring to figures.

In FIG. 1, a variable displacement compressor 50 has a cylinder block 51with a plurality of cylinder bores 51 a, a front housing 52 provided atone end of cylinder block 51, and a rear housing 53 provided to cylinderblock 51 via a valve plate device 54. A compressor main shaft 56 isprovided as a drive shaft across a crank chamber 55 formed by cylinderblock 51 and front housing 52, and an inclined plate 57 is disposedaround a central portion of the compressor main shaft. Inclined plate 57connects a rotor 58 fixed to compressor main shaft 56 and a connectingportion 59.

One end of compressor main shaft 56 extends to an outside through a boss52 a protruded toward an outside of front housing 52, and anelectromagnetic clutch 70 is provided around the boss 52 a via a bearing60. Electromagnetic clutch 70 comprises a rotor 71 provided around boss52 a, a magnet unit 72 contained in the rotor 71, and a clutch plate 73provided on one outer end surface of the rotor 71. One end of compressormain shaft 56 is connected to clutch plate 73 via a fastener 74 such asa bolt. A seal member 52 b is inserted between compressor main shaft 56and boss 52 a, thereby isolating between the inside and the outside.Further, the other end of compressor main shaft 56 is present incylinder block 51, and it is supported by a supporting member 78. Where,labels 75, 76 and 77 indicate bearings, respectively.

A piston 62 is inserted free to be slid into cylinder bore 51 a. Theperiphery of inclined plate 57 is disposed in a recessed portion 62 aformed at the inside of one end of piston 62, and by forming a structurefor engaging piston 62 and inclined plate 57 to each other via a pair ofshoes 63, the rotational movement of inclined plate 57 is transformedinto the reciprocating movement of piston 62.

A suction chamber 65 and a discharge chamber 64 are formed in rearhousing 53 separately from each other. Suction chamber 65 cancommunicate with cylinder bore 51 a via a suction port 81 provided onvalve plate device 54 and a suction valve (not shown), and dischargechamber 64 can communicate with cylinder bore 51 a via a discharge port82 provided on valve plate device 54 and a discharge valve (not shown).Crank chamber 55 communicates with a gas chamber 84 formed at a shaftend extended portion of compressor main shaft 56, through a gap betweencompressor main shaft 56 and bearing 77.

A displacement control valve 1 is provided in a recessed portion of arear wall of rear housing 53 in this variable displacement compressor50. This displacement control valve 1 is used for controlling adisplacement for discharge (displacement for compression, that is, astroke of piston 62). Displacement control valve 1 is provided at aportion in the discharge pressure supply passageway capable ofcommunicating from discharge chamber 64 to crank chamber 55, and a partof this discharge pressure supply passageway is formed from acommunication passage 66 to gas chamber 84 and a communication passage68 to discharge chamber 64. Further, a pressure relief passagewaycommunicating from crank chamber 55 to suction chamber 65 is provided,and a part thereof is formed from a communication passage 67.

As depicted in FIG. 2, displacement control valve 1 comprises a valvecasing 2; a bellows 6 as a pressure sensing means for sensing a suctionpressure which is disposed in a pressure sensing chamber 3 formed invalve casing 2, the inside of which is set at a vacuum condition and towhich springs 4 and 5 are disposed at inside and outside positionsthereof; an adjusting member 8 adjusting an amount ofexpansion/contraction of bellows 6, forming a part of valve casing 2 andprovided with holes 7 communication with communication passage 67 tosuction chamber 65; a transmission rod 10 of valve element 9 one end ofwhich is brought into contact with the upper end in the figure ofbellows 6 and which is supported slidably by valve casing 2; a valvepart 11 which is formed integrally with transmission rod 10 at the upperportion in the figure of transmission rod 10 and which opens and closescommunication passages 68 and 66 communicating between discharge chamber64 and crank chamber 55 of variable displacement compressor 50 inresponse to the expansion/contraction of bellows 6; a valve chamber 12in which valve part 11 is disposed; a partition wall 15 through which atransmission rod 13 at the other end of valve element 9 is disposed witha gap 14 with a non-contact structure giving no sliding resistance andwhich is fixed to valve casing 2; a pressure chamber 17 formedseparately at a position opposite to valve chamber 12 via partition wall15 and communicated to pressure chamber 3 side (suction pressure side)through a communication passage 16; and a solenoid 23. In the portion ofsolenoid 23, a further extended portion of transmission rod 13 of valveelement 9 is inserted into a fixed iron core 19 with a gap 18 ofnon-contact structure giving no sliding resistance, and a plunger 21urged by a spring 20 in a direction separate from fixed iron core 19 andfixed to the other end of valve element 9 and an electromagnetic coil 22excited for generating an electromagnetic force are provided. Solenoid23 controls the movement of plunger 21 and valve element 9 by increasingand decreasing the magnetic force of fixed iron core 19, which isgenerated by the electromagnetic force due to the excitation ofelectromagnetic coil 22, by adjusting the electromagnetic force, and bycontrolling the attraction force applied to plunger 21 in the axialdirection of the valve element due to the magnetic force of fixed ironcore 19. Plunger 21 and fixed iron core 19 are contained in a tubularmember 25 provided in housing 24, and although iron core 19 is fixed,plunger 21 is supported slidably in the axial direction of the valveelement. The above-described gap 14 formed between the innercircumferential surface of partition wall 15 and the outercircumferential surface of valve element 9 in the portion of partitionwall 15 forms a fixed orifice.

A pressure in crank chamber 55 acts in valve chamber 12, a pressure insuction chamber 65 acts on bellows 6, and the pressure in suctionchamber 65 acts also in pressure chamber 17 through pressure sensingchamber 3 and communication passage 16. Further, valve part 11 of valveelement 9 controls to open and close the discharge pressure supplypassageway communicating from discharge chamber 64 to crank chamber 55(valve chamber 12) on the way of the passageway. Furthermore, gap 14 inpartition wall 15 forms a fixed orifice provided on the way of thepressure relief passageway communicating from crank chamber 55 (valvechamber 12) to suction chamber 65 side (pressure chamber 17 side).Where, the discharge pressure from each of communication passages 66, 68acting on either side transmission rod 10 of valve element 9 cancel eachother out, and as a result, the discharge pressure does notsubstantially influence the movement in the axial direction of valveelement 9. Therefore, valve element 9 is controlled in opening/closingoperation substantially in response to the electromagnetic force and thepressure in the suction chamber acting on bellows 6.

In the above-described variable displacement compressor 50 havingdisplacement control valve 1, when a predetermined current is applied toelectromagnetic coil 22, an electromagnetic force acts to the surfacesfacing to each other of plunger 21 and fixed iron core 19, and a forceattracting plunger 21 toward fixed iron core 19 (a force in the valveclosing direction) acts. When this electromagnetic force becomes higherthan a certain level, valve part 11 is closed, and the communicationbetween discharge chamber 64 and crank chamber 55 is interrupted. Bythis, the gas in discharge chamber 64 is not introduced into crankchamber 55, and a gas flow occurs from crank chamber 55 toward suctionchamber 65 through fixed orifice (gap 14). Because this fixed orificehas a diameter necessary and enough to flow a blowby gas, whichgenerates when piston 62 compresses the gas, to suction chamber 65 side,the pressure in crank chamber 55 reduces to become substantially thesame pressure as that in suction chamber 65, and the compressor ismaintained at a maximum displacement and the pressure in suction chamber65 is gradually reduced.

When the pressure in suction chamber 65 is reduced down to apredetermined value, because bellows 6 expands and valve element 9operates in its opening direction, the gas in discharge chamber 64 isintroduced into crank chamber 55 side, and the displacement fordischarge is decreased by increase of a pressure difference betweencrank chamber 55 and suction chamber 65. By this, when the pressure insuction chamber 65 increases, because bellows 6 contracts and valveelement 9 operates in its closing direction, the pressure in crankchamber 65 is reduced, and the displacement for discharge is increasedby decrease of a pressure difference between crank chamber 55 andsuction chamber 65. Thus, in a case of a constant electromagnetic force,the opening degree of valve element 9 is adjusted so that the pressurein the suction chamber becomes a predetermined value, and thedisplacement for discharge is controlled.

In the above-described displacement control, because gap 14 formed atthe through portion of valve element 9 in partition wall 15 is formed asa flow passage, a non-contact structure may be easily formed betweenvalve element 9 and partition wall 15 by setting a large clearance inthis portion, and a sliding resistance is not generated in this portion.Further, in this embodiment, because gap 18 with a non-contact structurefor giving no sliding resistance is formed also between transmission rod13 of valve element 9 and fixed iron core 19, a sliding resistance isnot generated also in this portion. Therefore, valve element 9 issupported movably by totally two sliding parts of a lower-end sidesliding part between valve casing 2 and transmission rod 10 and anupper-end side sliding part between plunger 21 fixed to valve element 9and tubular member 25. The number of sliding parts is greatly reduced ascompared with totally four sliding parts in the conventional case, thesliding resistance is greatly decreased when valve element 9 is movedand controlled and a smooth movement of valve element 9 is ensured, andthe opening and closing operation of valve part 11 is carried out at ahigh accuracy by well following the variation of the electromagneticforce or the suction pressure. Therefore, a more smooth and stablehigh-reliability control of displacement for discharge may becomepossible. Further, because valve element 9 is supported at upper andlower parts substantially with two-point suspension, the supportingformation for making a rod slide may become stable.

Further, because gap 14 between the inner circumferential surface ofpartition wall 15 and the outer circumferential surface of valve element9 is formed as a fixed orifice, it is not necessary to provide the fixedorifice at another place, and as compared with the conventionalstructure, it becomes possible to simplify, in particular, theprocessing of the cylinder block and the vicinity thereof, and further,it is possible to simplify the processing of the compressor as a wholeand to reduce the cost thereof.

FIG. 3 depicts a displacement control valve 31 of a variabledisplacement compressor according to a second embodiment of the presentinvention. In this embodiment, a partition wall 32 for partitioningbetween valve chamber 12 and pressure chamber 17 is fixed to valveelement 9, for example, by press fitting, and a gap 34, which forms aflow passage from valve chamber 12 to pressure chamber 17 and forms anon-contact structure that does not give a sliding resistance relativeto the movement of valve element 9 in its axial direction, is formedbetween the outer circumferential surface of partition wall 32 and theinner circumferential surface of valve casing 33 of displacement controlvalve 31. This gap 34 forms a fixed orifice. Further, pressure sensingchamber 3 containing bellows 6 communicates with communication passage66 communicating to crank chamber 55 so that bellows 6 senses thepressure in the crank chamber. Valve chamber 12 communicates withpressure sensing chamber 3 through communication passage 35, therebyintroducing the pressure in the crank chamber into valve chamber 12.Pressure chamber 17 communicates with communication passage 67communicating to suction chamber 65 through communication passage 36,and the surface of pressure chamber 17 side of partition wall 32 isformed as a pressure receiving surface of the suction chamber side. Gap34 is disposed between pressure chamber 17 and valve chamber 12introduced with the pressure of the crank chamber side, as a fixedorifice provided on the way of a pressure relief passageway. The otherstructures are substantially the same as those depicted in FIG. 2, andthe explanation of those structures is omitted by giving FIG. 3 the samelabels as those of FIG. 2.

In displacement control valve 31 thus constructed, although bellows 6senses the pressure in the crank chamber, by enlarging the area forreceiving the suction pressure of partition wall 32 moved together withvalve element 9, the bellows operates to expand and contractsubstantially in response to the suction pressure, thereby moving andcontrolling valve element 9 in its axial direction, and a similarcontrol to that in displacement control valve 1 depicted in FIG. 2 maybe possible.

Also in this displacement control valve 31, valve element 9 is supportedmovably by totally two sliding parts of a lower-end side sliding partbetween valve casing 33 and transmission rod 10 and an upper-end sidesliding part between plunger 21 fixed to valve element 9 and tubularmember 25. The number of sliding parts is greatly reduced as comparedwith the conventional number and the sliding resistance is greatlydecreased, and a smooth movement of valve element 9 is ensured, and asmooth and stable high-reliability control of displacement for dischargemay become possible.

Further, because gap 34 between the outer circumferential surface ofpartition wall 32 and the inner circumferential surface of valve casing33 is formed as a fixed orifice, it is not necessary to provide thefixed orifice at another place, and as compared with the conventionalstructure, it becomes possible to simplify, in particular, theprocessing of the cylinder block and the vicinity thereof, and further,it is possible to simplify the processing of the compressor as a wholeand to reduce the cost thereof.

INDUSTRIAL APPLICATIONS OF THE INVENTION

In the present invention, a variable displacement compressor suitablefor use in an air conditioning system for vehicles, etc. can beprovided, and especially, a variable displacement compressor, in which asmooth and high-reliability operation can be carried out at the portionof the displacement control valve and the processing of which can besimplified as a whole, may be provided.

1. A variable displacement compressor having a discharge chamber, asuction chamber and a crank chamber, said compressor comprising adisplacement control valve disposed at a position in a dischargepressure supply passageway capable of communicating with said crankchamber from said discharge chamber, and a fixed orifice provided at aposition in a pressure relief passageway communicating with said suctionchamber from said crank chamber, said displacement control valve beingcontrolled in opening/closing operation to regulate a pressure in saidcrank chamber to control a piston stroke, wherein said displacementcontrol valve further comprises a pressure sensing member being expandedand contracted by sensing a pressure in said suction chamber or saidcrank chamber, a valve element one end of which is brought into contactwith said pressure sensing member and which has a valve part opening andclosing a valve hole formed in said discharge pressure supply passagewayin response to an expansion/contraction of said pressure sensing member,a valve chamber in which said valve part is disposed and to which apressure in said crank chamber acts, a fixed partition wall disposedaround said valve element at a position in an axial direction of saidvalve element, a pressure chamber which is partitioned from said valvechamber by said fixed partition wall and to which a pressure in saidsuction chamber acts, and a solenoid provided to the other end of saidvalve element and capable of controlling an opening degree of said valvepart by increase/decrease of an electromagnetic force, and said pressurerelief passageway from said valve chamber to said pressure chamber isformed by a gap between said fixed partition wall and said valve elementfor forming a non-contact structure which does not give a slidingresistance relative to a movement of said valve element in its axialdirection, wherein said pressure relief passageway continuously is open.2. The variable displacement compressor according to claim 1, whereinsaid gap forms said fixed orifice.
 3. The variable displacementcompressor according to claim 1, wherein said fixed partition wall isfixed at a valve casing side of said displacement control valve, andsaid gap is defined between an inner circumferential surface of saidfixed partition wall and an outer circumferential surface of said valveelement.
 4. The variable displacement compressor according to claim 1,wherein said fixed partition wall is fixed to said valve element, andsaid gap is defined between an outer circumferential surface of saidfixed partition wall and an inner circumferential surface of a valvecasing of said displacement control valve.
 5. The variable displacementcompressor according to claim 1, wherein said solenoid comprises anelectromagnetic coil excited for generating an electromagnetic force, afixed iron core for generating a magnetic force by excitation of saidelectromagnetic coil, and a plunger attracted and moved to fixed ironcore side by said magnetic force of said fixed iron core, the other endof said valve element is fixed to said plunger, said plunger is heldslidably in an axial direction of said valve element, and a gap isdefined between said fixed iron core and said valve element for forminga non-contact structure which does not give a sliding resistancerelative to a movement of said valve element in its axial direction.